Production of acrylonitrile



United States Patent US. Cl. 260-4653 12 Claims ABSTRACT OF THE DISCLOSURE Acrylonitrile is produced by a non-catalytic process by contacting acetonitrile and an aliphatic hydrocarbon in the presence of iodine, chlorine or combinations thereof.

The present invention relates to a process for the production of acrylonitrile. More particularly, the present invention relates to a new and improved non-catalytic process for the direct synthesis of acrylonitrile from acetonitrile and aliphatic hydrocarbons.

Acrylontrile is among the most valuable monomers available to the polymer industry for producing useful polymeric products. This valuable monomer is used in the preparation of synthetic fibers, synthetic rubbers and for other useful plastic products. Presently, most of the acrylonitrile is produced by such catalytic processes as the catalytic reaction of acetylene and hydrogen cyanide and the reaction of ammonia and propylene. While the known catalytic processes have proven very effective in producing acrylonitrile, the demand for acrylonitrile is so great as to make desirable the development of new and additional processes for producing acrylonitrile. Also, in general, the catalysts most often used in acrylonitrile production are relatively expensive in cost and handling. For these and other reasons, it would be advantageous to have means of producing acrylonitrile without the use of a catalyst.

In copending application Ser. No. 604,626, filed Dec. 27, 1966, a new non-catalytic process for the preparation of acrylonitrile has been disclosed and claimed. The process involves the thermal reaction of acetonitrile and aliphatic hydrocarbon to produce acrylonitrile in relatively good yields. While this process represents a significant advancement in the art of preparing acrylonitrile, it would represent an additional advancement in the art to provide an improvement in the process described and claimed in the copending application.

It is an object of the present invention to provide a new and novel process for the production of acrylonitrile. Another object of the present invention is to provide a new and improved non-catalytic process for the production of acrylonitrile. An additional object of the present invention is to provide a new and improved process for the production of acrylontrile by the non-catalytic direct reaction of acetonitrile and aliphatic hydrocarbons. A further object of the present invention is to provide a novel improvement in the process of producing acrylonitrile by the noncatalytic reaction of acetonitrile and aliphatic hydrocarbons. Additional objects will become apparent from the following description of the invention herein disclosed.

The present invention, which fulfills these and other objects, is a process for the preparation of acrylonitrile which comprises subjecting acetonitrile and an aliphatic hydrocarbon to a temperature within the range of 750 to 1000 C. for a period of 0.1 to seconds in the absence of a catalyst and in the presence of a minor amount of a promoting agent selected from the group consisting of iodine, chlorine and combinations thereof. By this process, significant quantities of acrylonitrile are produced. Further, the acrylonitrile is produced without the aid of a catalyst. Since no catalyst is required, the present process results in a reduction of the expense required for catalyst Patented June 10, 1969 purchase and handling. Additionally, the process of the present invention provides a significant improvement in acrylonitrile yields over those obtained by the reaction of acetonitrile and an aliphatic hydrocarbon without the use of the herein-defined promoting agents.

In order to further describe as well as to demonstrate the present invention, the following examples are presented. These examples are not to be construed as in any manner limiting the present invention.

EXAMPLE I A mixture of substantially equimolar quantities of acetonitrile and methane was passed through a reactor tube having a length of 12 inches and an internal diameter of one inch. Iodine, as a promoting agent, was introduced into the reactor tube concurrently with the mixture of acetonitrile and methane. The amount of iodine represented 1 mole percent of the acetonitrile-aliphatic hydrocarbon mixture. The temperature within the reaction tube was approximately 900 C. and the residence time of the reactants within the reaction zone was 3 seconds. The effluent from the reactor tube was passed through a condenser and a liquid product obtained. This liquid product was found to contain 8% by weight of acrylonitrile with the remainder of the liquid product being primarily unreacted acetonitrile.

EXAMPLE II Example I was substantially repeated with the exception that the amount of iodine represented 2.5 mole percent of the acetonitrile-aliphatic hydrocarbon mixture and the temperature was 940 C. On analysis, the liquid product of this run was found to contain approximately 18% by weight acrylonitrile, the majority of the remainder of the liquid product being unreacted acetonitrile.

EXAMPLE III Example II was substantially repeated with the exception that chlorine was used as the promoting agent in an amount representing 11.0 mol percent of the acetonitrilealiphatic hydrocarbon mixture, the temperature was 950 C. and the residence time was 2 seconds. The liquid product was found to contain approximately 8% by weight acrylonitrile, the remainder of the liquid product being primarily unreacted acetonitrile.

EXAM'PLE IV Example III was substantially repeated with the exception that the amount of chlorine represented 26.5 mole percent of the acetonitrile-aliphatic hydrocarbon mixture. The liquid product was found to contain 12% by weight acrylonitrile, the remainder of the liquid product being primarily unreacted acetonitrile.

EXAMPLE V Example III was again substantially repeated with the exception that nitrogen was introduced as an inert diluent. The liquid product was found to contain 10% by weight acrylonitrile, the remainder of the liquid product being primarily unreacted acetonitrile.

EXAMPLE VI Example I was substantially repeated with the exception that no iodine or chlorine was added as a promoting agent. The liquid product was found to contain approximately 3% by weight acrylonitrile, the remainder of the liquid product being primarily unreacted acetonitrile.

EXAMPLE VII Example I was again substantially repeated with the exception that no iodine or chlorine was added as a promoting agent and the temperature was 950 C. The liquid product was found to contain 5% by weight acrylonitrile,

the remainder of the liquid product being primarily unreacted acetonitrile.

Comparison of Examples I through V, carried out in accordance with the present invention, with Examples VI and VII, not carried out in accordance with the present invention, clearly demonstrates the advantages to be obtained from the process of the present invention. For example, in Example I an 8% yield of acrylonitrile is obtained as compared to a 3% yield in Example VI. Also, an 18% yield was obtained in Example II while under similar conditions without a promoting agent in Example VII, a yield of was obtained.

To further demonstrate the efficiency of the process of the present invention, Examples I and VI are substantially repeated with ethane as the aliphatic-hydrocarbon. Improved yields of acrylonitrile are obtained by the repetition of Example I as compared with the repetition of Example VI. Similar improvements are obtained when propane, butane, and the like are substituted for the methane of the above examples.

The promoting agents employed in the process of the present invention include molecular iodine, chlorine and combinations thereof. These promoting agents may be used in almost any concentration but usually are used in an amount of 0.5 to 100 mole percent of the acetonitrile charged. In most instances, larger amounts of chlorine are employed than iodine. For example, when using iodine, the amount used usually will be within the range of 1 to 30 mole percent of the acetonitrile charged, though greater amounts may be employed if desired, whereas when using chlorine, the amount used most often is within the range of to 60 mole percent of the acetonitrile charged. In the preferred practice of the present invention, iodine in an amount of 2 to 15 mole percent of the acetonitrile charged is used as the promoting agent.

The aliphatic hydrocarbons useful in the process of the present invention include both the saturated and unsaturated aliphatic hydrocarbons. These alphiatic hydrocarbons may be straight chain or branched chain. If unsaturated, the aliphatic hydrocarbons may be terminally or internally unsaturated. The molecular weight of the aliphatic hydrocarbons may vary substantially ranging from methane up to aliphatic hydrocarbons having 30 to 40 carbon atoms and higher. Choice of molecular weight of aliphatic hydrocarbon for use in the process of the present invention is primarily a matter of practicality. Among the aliphatic hydrocarbons which may be used in carrying out the process of the present invention are the following non-limiting examples: methane, ethane, propane, propylene, n-butane, n-butenes, isobutane, isobutenes, n-pentane, n-pentenes, n-hexane, n-heXenes, Z-methyl pentane, B-methyl pentane, Z-methyl pentenes, n-heptane, n-heptenes, methyl heptanes, methyl heptenes, dimethyl heptanes, methyl ethyl heptenes, n-octane, n-octenes, nnonane, n-nonenes, and the like. As a practical matter, the'aliphatic hydrocarbons used in the process of the present invention are the parafiin and olefin hydrocarbons of less than carbon atoms. In the preferred practice of the present invention, the aliphatic hydrocarbons are parafiin hydrocarbons of l to 10 carbon atoms and olefin hydrocarbons of 3 to 10 carbon atoms.

The acetonitrile and the aliphatic hydrocarbons most often are introduced into the reaction zone in a molar ratio of acetonitrile to aliphatic hydrocarbon within the range of 10:1 to 1:10. The preferred mol ratio will vary to some extent with the molecular weight of the aliphatic hydrocarbons employed. In a general sense, it may be said that higher ratios of acetonitrile to aliphatic hydrocarbons may be used as the molecular weight of the hydrocarbon increases. This results from the fact that at the temperatures at which the process is carried out, some cracking of the aliphatic hydrocarbons will usually take place. Therefore, with higher molecular weight aliphatic hydrocarbons, the cracking of one mol of such hydrocarbon may result in the formation of two or more mols of lower molecular weight aliphatic hydrocarbons available for reaction with the acetonitrile to form acrylonitrile. With the preferred aliphatic hydrocarbons, herein above defined, acetonitrile to aliphatic hydrocarbon mol ratios within the range of 5:1 to 1:5 are usually employed in the practice of the present invention.

The temperatures at which the process of the present invention is operated, generally, are within the range of 750 to 1000 C. At temperatures below 750 C., reaction is below practical limitations. Above 1000 C., cracking of the reactants becomes excessive. Within the above defined temperature range, it has been found that the optimum reaction temperature decreases slightly with the increase in molecular weight of the aliphatic hydrocarbon. In the preferred practice of the process of the present invention, temperatures within the range of 850 to 975 C. are most often used.

The pressure at which the process of the present invention is operated is not particularly critical and may be varied over wide ranges. The pressure may be subatmospheric, atmospheric or superatmospheric. Most often, the pressure at which the process of the present invention is operated will be within the range of 5 to p.s.i.a. As a practical matter, the present invention is usually operated at or near atmospheric pressure, i.e., 14.5 to 20 p.s.i.a.

In operating the present process, the residence time of the reactants within the reaction zone most often is within the range of 0.1 to 20 seconds. The optimum residence time will vary according to temperatures, lower residence time being used with higher temperatures and conversely, longer residence time being used with lower temperatures. In the preferred practice of the process of the present invention, a residence time of 1 to 10 seconds is most often employed.

In carrying out the process of the present invention, it is often desirable to carry out the reaction of the acetonitrile and aliphatic hydrocarbon in the presence of a diluent. Such a diluent is inert to the chemical reaction taking place within the reaction zone. Exemplary of materials which may be used as diluents are nitrogen, helium, argon, carbon dioxide, and the like. Among the preferred diluents are nitrogen and argon. When a diluent is used, it may be used in practically any concentration. However, as a practical matter, the diluent is most often present in a mol ratio of diluent to combined acetonitrile and ailphatic hydrocarbon within the range of 0.25:1 to 3:1.

What is claimed is:

1. A process for the preparation of acrylonitrile which comprises subjecting acetonitrile and an aliphatic hydrocarbon selected from the group consisting of parafiins of l to 10 carbon atoms and olefins of 3 to 10 carbon atoms to a temperature within the range of 750 to 1000 C. for a period of 0.1 to 20 seconds in the absence of a catalyst and in the presence of a promoting agent selected from the group consisting of molecular iodine, molecular chlorine and combinations thereof wherein the mol ratio of acetonitrile to aliphatic hydrocarbon is within the range of 10:1 to 1:10.

2. The process of claim 1 wherein the temperature is within the range of 850 to 975 C.

3. The process of claim 1 wherein the pressure is within the range of 5 to 100 p.s.i.a.

4. The process of claim 1 wherein the residence time is within the range of 1 to 10 seconds.

5. The process of claim 1 wherein the acetonitrile and aliphatic hydrocarbon are subjected to the reaction conditions in the presence of an inert diluent.

6. The process of claim 5 wherein the inert diluent is selected from the group consisting of nitrogen, helium, argon, carbon dioxide and mixtures thereof.

7. The process of claim 1 wherein the promoting agent is employed in an amount of 0.5 to 100 mol percent of the acetonitrile charged.

8. The process of claim 7 wherein the promoting agent is iodine and is employed in an amount of 1 to 30 mol percent of the acetonitrile charged.

5 6 9. The process of claim 8 wherein the aliphatic hydro- References Cited 15 methane- UNITED STATES PATENTS 10. The process of claim 7 wherein the promoting agent is chlorine and is employed in an amount of 15 to 60 mol 3,055,738 9/1962 Krebaumpercent of the acetonitrile charged.

11. The process of claim 10 wherein the aliphatic hydro- 5 JOSEPH BRUST Exammer' carbon is methane. U S C1 X R 12. The process of claim 1 wherein the aliphatic hydrocarbon is methane. 260465.3 

